Propeller-type fan blade



G. s. FABER PROPELLER-TYPE FAN BLADE July 27, 1954 2 Sheets-Sheet 1 Filed Sept. 7. 1950 I fifgnfar 1 July 27, 1954 a FABER 2,684,723

PROPELLERTYPE FAN BLADE Filed Sept, 7, 1950 2 Sheets-Sheet 2 Patented July 27, 1954 UNITED STATES PATENT OFFICE PROPELLER-TYPE FAN BLADE Guy S. Faber, Chicago, Ill.

Application September 7, 1950, Serial No. 183,566

Claims. (01. 170-166) This invention relates to fans and more particularly to air circulating fans.

It is the general object of this invention to produce a new and improved fan.

One of the features of this invention is the employment of a propeller of unique design and construction which is capable of moving a large volume of air with a minimum amount of power.

Another feature of the invention is the provision in a circulating fan of a venturi ring positioned immediately adjacent the discharge side of the fan and located at the point of maximum discharge velocity.

Another feature of this invention is the provision of a second venturi which surrounds the outer tip of the propeller and which cooperates with the first venturi in a manner to produce a large movement of air through the tip area of the propeller by eliminating the vortices which normally would otherwise occur.

A further feature of the invention is the provision of a propeller made up of two blade segments, the inner segment having a predetermined pitch and extending only a part of the distance from the hub to the outer tip and a second blade segment connected to but axially offset from the first segment and extending from the outer tip of the propeller only a part of the distance to the hub.

Another feature of the invention is the production of a propeller as described in the preceding paragraphs which has a maximum air discharge area located approximately at the tip of the inner blade segment.

Yet, another feature of the invention is the combination of a propeller of the type described in the preceding paragraphs with a first venturi located on the discharge side of the fan approximately at the location of the tip of the inner blade segment together with a Venturi shroud which surrounds the tip of the outer blade segment, which combination produces a fan capable of propelling, in effect, two air streams, one driven by the inner blade segment and the other by the outer blade segment, so that the entire propeller area performs a useful function in moving air. This is in contrast to the ordinary form of construction in which approximately the outer one-third of the propeller blade produces only air vortices around the propeller tips and therefore agitates rather than propels air.

Other and further features of the invention will become apparent from the following description and drawings in which:

Fig. 'l is a front elevation of the fan of this invention showing the propeller and a portion of the inner and outer venturi;

Fig. 2 is a side elevation of the apparatus shown in Fig. 1;

Fig. 3 is a rear elevation of the propeller of this invention;

Fig. 4 is an enlarged detailed view of one-half of the propeller shown in the previous figures, and

Figs. 5 to 11, inclusive, are sectional views taken along lines 5-5 to Hl I, respectively, of Fig. 4.

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will be herein described in detail one specific embodiment with the understanding that the present description is to be considered as an example of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

The fan of this invention includes a hub 29 to which is secured an inner blade segment having the portions 22 and 22a on either side of the hub 20. The inner blade segment extends from the hub only a part of the distance to the outer tip of the propeller. Secured to the inner blade segment is an outer blade segment made up of the portions23 and 23a which extend from the outer tipof the propeller only a part of the distance to the hub.

The portions 22 and 22a of the inner blade segment are identical to each other as are the portions 23 and 23a of the outer blade segment and hence, to simplify the disclosure, only the portions 22 and 23 will be described in detail, it being understood that the portions 22a and 23a making up the other half of the blade segments are identical in construction.

The portion 22 is pitched from its leading edge 24 to its trailing edge 25 substantially uniformly from its inner to its outer end. The preferred pitch is approximately If desired, the small area 88 of the portion 22 close to the hub 2i! may be given a slightly increased pitch in order to increase the flow of air over an electric driving motor (not shown) secured by means of a shaft in an opening 26 provided in the hub. This increased flow of air over the motor aids in maintaining it at proper operating temperature and to prevent overheating.

The front surfaces 22' and 23 of inner and outer blade segments 22 and 23 have a concave configuration as shown in Figures 5-11.

The outer blade segment 23 is preferablypro vided with substantially the same pitch as the inner blade segment 22, but the entire outer segment is oifset from the inner segment axially of the propeller. The oifset is in the direction of 180 to the direction of air flow over the propeller and thus, in effect, the outer blade segment leads the inner blade segment. The amount of offset depends somewhat on the speed at which the propeller is to be operated. For normal operations with the fan at from 1,000 to 2,000 R. P. M., the amount of offset is from to /8 inch. With the slower speed fans the oifset can be increased to as much as inch although where the offset is this large the juncture between the inner and outer segments should be a curve rather than a step.

The leading edge 2? of the outer blade segment is secured to the trailing edge of the inner blade segment along the line indicated along that portion of its leading edge lying within the outer tip 28 of the inner segment and the convex trailing edge all of the outer segment joins the trailing edge 25 of the inner segment at ill. The portion 2? of the leading edge of the outer segment, which extends beyond the tip 28, is concave so as to reduce the area of the outer segment in that portion lying between the tip 23 of the inner segment and the tip of the outer segment. Surrounding the tip 29 of the outer blade segment is a Venturi shroud 36 comprising a first venturi 3| having a circular opening 32 axially spaced from the propeller in the direction cpposite to the direction of air flow and narrows axially to its end 33 located radially opposite the tip 2%. A step portion 3a connects the inner end 33 of the first venturi with a second venturi 35 which has a discharge opening 35 axially displaced from the tip 29 in the direction in which the air is moving.

A Venturi ring 37 is secured to the Venturi shroud 30 by rods (not shown) and is located at the tip 28 of the inner blade segment on the discharge side to the propeller.

In the normal propeller approximately the outer one-third of the blade, that is that portion of the blade extending from the tip one-third of the distance toward the hub or center, is surrounded by vortices of air as the blade is rotated. Thus the air around the outer portion of the propeller is not being propelled or projected as desired, but is merely being agitated. Thus the tip area of a propeller, which is rotating at the greatest lineal speed and should therefore propel the greatest volume of air, has a zero efiiciency in the normal construction. In the propeller of this invention, the tip 28 of the inner blade segment is not lost inasmuch as that area, while being the outer tip of the inner blade segment, is not the outer tip of the entire propeller. Thus the area of maximum flow is located at the tip of the inner blade segment.

By providing the Venturi shroud 3E and the Venturi ring Si, I further provide an area indicated by A located between the tips of the inner and outer segments and immediately adjacent the point of maximum air fiow in which the pressure is reduced due to the Venturi action.

This reduced pressure in the area A serves to draw air surrounding the back of the fan into this area, and the air so drawn is propelled by the portion of the outer blade segment between the tips 28 and 23. Thus the construction disclosed serves not only to eliminate the vortices around the tip 28, but the vortices around and inwardly from the tip 29 are also eliminated. In practice I have found that the venturis positioned as indicated so increase the flow of air to the outer portion of the outer blade segment as to require the reduction of the area of that segment so as not to overload the driving motor. Thus it will be noted that the leading edge 21" of the outer blade segment is concave so as to reduce the area of that portion of the segment.

As previously stated, the highest velocity of air is achieved approximately at the tip 253 of the inner blade segment, and a column of air from that tip to the hub is projected forwardly from the fan. A second column of air is also projected forwardly from the area A although the second column is moving at a somewhat slower velocity than the first. These two streams or columns of air merge some distance in front of the fan to produce a single column of comparatively large volume and velocity.

In actual tests, a 24 inch diameter propeller of normal construction and driven by a T horsepower motor operating at a speed of 750 R. P. M. delivered 2,150 cubic feet of air per minute, with the motor drawing 3.75 amps and 280 watts. The conventional propeller and fan construction so overloaded the motor as to reduce its speed to 250 R. P. M. At this speed and with this load the motor would have an extremely short life. The same motor was connected to a propeller and fan of the type described in this application and operated at its normal speed of 1,600 B. P. M., drawing 2.20 amps and 260 watts. 3,980 cubic feet of air per minute were delivered.

An additional feature of the fan is the fact that the inner and outer blade segments may be made of dififerent colored material. Thus the inner blade segment may be chrominum plated and the outer blade segment colored gold. While this contributes nothing to the efficiency of the fan, it does add to its appearance inasmuch as the fan, when operating, shows an inner silver ring, an outer gold ring, and an intermediate area where the silver and gold blend together. The results are quite attractive.

I claim:

1. A propeller having a hub, a first blade segment having a concave front surface and extending outwardly from the hub more than half, but less than all of the distance to the outer tip of the propeller, the leading edge of the first seg ment having a concave configuration and the trailing edge thereof having a convex configuration, and a second blade segment having a concave front surface of substantially the same pitch as the front surface of the first segment and extending inwardly from the outer tip of the propeller more than half, but less than all the distance to the hub, the trailing edge of the second segment having a convex configuration and joining the trailing edge of the first segment along said convex configuration, the leading edge of the second segment having two portions each having a concave configuration, the first portion of the leading edge of the second segment being more concave than the leading edge of the first segment and extending inwardly from the outer tip of the propeller to join the leading edge of the first segment at the outer tip thereof and the second portion of the leading edge of the second. segment being joined to the trailing edge of the first segment from the outer tip of the first segment inwardly and joining the trailing edge of the second segment, the second segment being axially offset from the first segment along the juncture therebetween and in a direction opposite to the flow of air from the propeller, the length of the propeller being many times the width thereof.

2. A propeller having a hub, a first blade segment having a concave front surface and extend ing outwardly from the hub more than half, but less than all of the distance to the outer tip of the propeller, the leading edge of the first segment having a concave configuration and the trailing edge thereof having a convex configuration, and a second blade segment having a concave front surface and extending inwardly from the outer tip of the propeller more than half, but less than all of the distance to the hub, the trailing edge of the second segment having a convex configuration and joining the trailing edge of the first segment along said convex configuration, the leading edge of the second segment having two portions each having a concave configuration, the first portion extending inwardly from the outer tip of the propeller to join the leading edge of the first blade segment at the outer tip thereof and. the second portion of the leading edge of the second segment being joined to the trailing edge of the first segment from the outer tip of the first segment inwardly and joining the trailing edge of the second segment, the second segment being axially offset from the first segment along the juncture therebetween and in a direction opposite to the fiow of air from the propeller.

3. A propeller having a hub, a first blade segment having a concave front surface and extending outwardly from the hub only a portion of the distance to the outer tip of the propeller, the leading edge of the first segment having a concave configuration and the trailing edge thereof having a convex configuration, and a second blade segment having a concave front surface and extending inwardly from the outer tip of the pro peller only a portion of the distance to the hub, the trailing edge of the second segment having a convex configuration and joining the trailing edge of the first segment along said convex configuration, the leading edge of the second segment having two portions each having a concave configuration, the first portion of the leading edge of the second segment being more concave than the leading edge of the first segment and extending inwardly from the outer tip of the propeller to join the leading edge of the first blade segment at the outer tip thereof and the second portion of the leading edge of the second segment being joined to the trailing edge of the first segment from the outer tip of the first segment inwardly and joining the trailing edge of the second segment, the second segment being axially offset from the first segment in a direction opposite to the flow of air from the propeller.

4. A propeller having a hub, a first blade segment extending outwardly from the hub only a portion of the distance to the outer tip of the propeller, the leading edge of the first segment having a concave configuration and the trailing edge thereof having a convex configuration, and a second blade segment extending inwardly from the outer tip of the propeller only a portion of the distance to the hub, the trailing edge of the second segment having a convex configuration and joining the trailing edge of the first segment, the leading edge of the second segment having two portions each having a concave configuration, the first portion extending inwardly from the outer tip of the propeller to join the leading edge of the first blade segment at the outer tip thereof and the second portion of the leading edge of the second segment being joined to the trailing edge of the first segment from the outer tip of the first segment inwardly and joining the trailing edge of the second segment, the second segment being axially offset from the first segment in a direction opposite to the flow of air from the propeller.

5. A propeller having a hub, a first blade segment extending outwardly from the hub only a portion of the distance to the outer tip of the propeller, the leading edge of the first segment having a concave configuration and the trailing edge thereof having a convex configuration, and a second blade segment extending inwardly from the outer tip of the propeller only a portion of the distance to the hub, the trailing edge of the second segment having a convex configuration and joining the trailing edge of the first segment, the leading edge of the second segment having two portions each having a concave configuration, the first portion extending inwardly from the outer tip of the propeller to join the leading edge of the first blade segment at the outer tip thereof and the second portion of the leading edge of the second segment being joined to the trailing edge of the first segment from the outer tip of the first segment inwardly and joining the trailing edge of the second segment, the second segment being axially offset from the first segment.

6. A propeller having a hub, a first blade segment extending outwardly from the hub only a portion of the distance to the outer tip of the propeller, the leading edge of the first segment having a concave configuration and the trailing edge thereof having a convex configuration, and a second blade segment extending inwardly from the outer tip of the propeller only a portion of the distance to the hub, the trailing edge of the second segment having a convex configuration and joining the trailing edge of the first segment, the leading edge of the second segment having two portions each having a concave configuration, the first portion extending inwardly from the outer tip of the propeller to join the leading edge of the first blade segment at the outer tip thereof and the second portion of the leading edge of the second segment being joined to the trailing edge of the first segment from the outer tip of the first segment inwardly and joining the trailing edge of the second segment.

7. A propeller having a hub, a first blade segment extending outwardly from the hub only a portion of the distance to the outer tip of the propeller, the trailing edge of the first segment having a convex configuration, and a second blade segment extending inwardly from the outer tip of the propeller only a portion of the distance to the hub, the trailing edge of the second segment having a convex curve and joining the trailing edge of the first segment, a portion of the leading edge of the second segment having a concave configuration and being joined to the trailing edge of the first segment and joining the trailing edge of the second segment, the second segment being axially offset from the first segment.

8. A propeller of the character described in claim 4 adapted to be operated at a speed between 1,000 R. P. M. and 2,000 R. P. M. and in which the axial offset is of the order of inch to inch.

9. A propeller of the character described in claim 4 adapted to be operated at a speed less than 1,000 R. P. M. and in which the axial offset is of the order of 1 inch.

10. A propeller of the character described in 7 claim 3 wherein the outer tip of the propeller Number leads the outer tip of the first blade segment. 2,370,652 2,390,804 References Cited in the file of this patent 51 7 UNITED STATES PATENTS 5 2,536, 0 2,576,294 Number Name Date D. 138,866 Orsett Sept. 19, 1944 1,123,202 Amnelius Dec. 29, 1914 1,815,529 Shurtleff July 21, 1931 3 1,993,158 Funk Mar.5,1935

Ballentine Feb! 11, 1941 Name Date Frisbie Mar. 6, 1945 McLean Dec. 11, 1945 Griese July 11, 1950 Herrman Jan. 2, 1951 Geraci Nov. 27, 1951 FOREIGN PATENTS Country Date Great Britain of 1883 

